The present invention relates to a fuel tank for heavy vehicles, for example a lorry. The invention relates in particular to a fuel tank of the type which is mounted to a vehicle frame by means of at least one supporting bracket or the like, said vehicle frame extending in the longitudinal direction of the vehicle.
Fuel tanks for heavy vehicles, particularly heavy-goods vehicles, are generally cylindrically designed having two end gables and an intermediate casing surface. Two main types of fuel tanks are available on the market, wherein one of the tanks is circularly cylindrical hereinafter called the circular tankxe2x80x94and the other tank is rectangularly cylindricalxe2x80x94hereinafter called the rectangular tank.
Traditionally, the circular tank is the dominant tank type in, among other countries, the USA, where the xe2x80x9croundxe2x80x9d tanks are considered to constitute an essential part of the overall appearance of the lorry and therefore, for reasons of appearance, often are chromium-plated on the outside. Thus, rectangular tanks are as yet hard to sell on the american market, even though an increased use of so-called chassis skirts along the sides of the chassisxe2x80x94said skirts covering the tanks so that they can""t be seen from the sides of the vehiclesxe2x80x94can be noted there too. The chassis skirts are conducive to a reduced air resistance for the vehicle, while at the same time they give the vehicle a more integrated, design-friendly visual impression. An advantage as regards a circular tank is that it, owing to its round tank base form, has a minimal rest volume, i.e. the volume which never can be sucked up from the tank on account of the fuel suction tube of the tank of necessity being situated at a certain distance from the tank base.
An additional advantage as regards the circular tank is that it is mounted to the vehicle frame by means of two comparatively compactxe2x80x94and by that weight-savingxe2x80x94supporting brackets which also provide a satisfactory road clearance by means of being constructed as a vertical cradle having a partly circular contact surface for the tank. The supporting brackets are provided with attachments for straps, by means of which attachments the circular tank is forced into towards the cradles of the supporting brackets.
A disadvantage as regards the circular tank is that it has a tendency to rotate in its mounting during the vibrations and shakings of the driving and, as a result of this, to expose the fuel lines and the armatures to large strains. In fact, in many countries it is required that circular tanks also are provided with side-collision protections outside the tank, toward the vehicle sides, seeing that otherwise, it is feared, pedestrians or colliding smaller vehicles may end up under the chassis of the heavy vehicle in the event of a collision. However, no side-collision protections are required when rectangular tanks are used, which is due to the fact that their essentially plane sides against the vehicle sides themselves are considered to be adequate in this respect.
On the european market, the rectangular tank is instead the dominating tank type, which principally is due to the fact that it holds a comparatively larger fuel volume than the circular tank. Maximizing the fuel volume of the tank is also particularly important on, for example, the european market, where regulations prescribed by european law limits the maximum length allowed for the so-called vehicle equipage length, including the vehicle cabin and the load carrier part. Consequently, what is aimed for in Europe is the largest possible tank volume for the smallest possible vehicle length, which, thus, is the principal reason for the rectangular tank being demanded to such an extent. This circumstance is particularly noticeable as regards the decidedly most common heavy-goods vehicle, the semitrailer, which consists of a towcar and a separate load carrier partxe2x80x94i.e. the trailer. In the USA, however, the comparatively smaller fuel volume of the circular tank is not such a big problem, since the regulations prescribed by the US law only regulates the maximum length allowed for the actual load carrier part, wherein it is easy to instead make the tank that is situated on the towcar longer and thereby obtain the desired fuel volume. An additional advantage as regards the rectangular tank is that it, by means of its very rectangular form, does not present any tendencies to rotate in its mounting during driving, as is the case with the circular tank, which has been mentioned above.
However, one disadvantage as regards the rectangular tank is that it, due to its essentially plane tank base, has a comparatively large rest volume. Another disadvantage is that the tank is mounted to the vehicle frame by means of two L-shaped supporting brackets, which, on the one hand, are heavier than the corresponding partly circular supporting brackets for a circular tank and, on the other hand, result in an inferior road clearance and/or reduced fuel volume, which is due to the horizontal section of the L, which generally has a height of approximately 10 cm. Thus, the visual impression regarding the volume optimization of a rectangular tank as compared to a circular tank is somewhat illusory, which is due to the fact that a height that is equivalent to 10 cm is instead utilized for valuable fuel volume in the circular tank. Therefore, the actual difference in fuel volume between the two tank types is not as large as the eye might be lead to believe.
For the above-mentioned reasons, manufacturers of heavy-goods vehicles provide rectangular as well as circular tanks for their vehicles, all according to the demand. As has been mentioned above, the different tank types require completely different types of supporting brackets. In the end, simulateously providing both circular and rectangular tanks results in higher costs for the manufacturer as regards both construction and production, as compared to instead providing only one single tank type.
The object of the present invention is to provide a fuel tank for heavy vehicles, said fuel tank offering a combination of the most important advantages of a circular as well as a rectangular fuel tank. Thus, a fuel tank is provided which holds a comparatively large fuel volume, a small rest volume and a satisfactory road clearance, wherein the design of the fuel tank at the same time eliminates tendencies to rotations in the mounting and the need of additional side-collision protections along the sides of the tank.
Thus, the invention relates to a fuel tank for heavy vehicles, said fuel tank being adapted for mounting to a vehicle frame by means of at least one supporting bracket which discloses a partly circular contact surface against said fuel tank, wherein the tank comprises two end gable sections and an essentially cylindrical casing section which extends between said end gable sections. The fuel tank comprises a first section which is partly circular and faces towards the vehicle frame and is adapted for bearing against said partly circular contact surface on the supporting bracket, and a second section which is essentially rectangular and faces away from the vehicle frame.
Furthermore, the invention makes it possible to utilize supporting brackets of the same sort on all the vehicles, regardless of whether they are intended for markets on which either circular or rectangular tanks traditionally are demanded. Consequently, the constructional and the productional costs for the manufacturer can be substantially reduced.
Furthermore, the fuel tank according to the invention provides the same visual impression regarding the volume optimization as a rectangular tank, without the tank suffering from the drawbacks of the rectangular tank.
Other features and advantages of the invention will be apparent from the following description of a preferred embodiment and from the claims.